The present invention is related to a high pressure pump and a coupling structure of a high pressure pump, and more particularly, to a high pressure pump having an intermediate member, which includes a cylinder body to pressurize fluid in a pressurizing chamber by reciprocating a plunger in a cylinder and which is arranged between two clamping members, the intermediate member being clamped by a clamping bolt, which extends between the two clamping members, by means of the clamping members.
For example, Japanese Laid-Open Patent Publication No. 11-210598 discloses a high pressure fuel pump used for an engine such as a cylinder injection type gasoline engine. In the high pressure fuel pump, an intermediate member, such as a sleeve (corresponding to a “cylinder body”), is held by members such as brackets along the axial direction and clamped to a casing by a clamping bolt to improve the machining characteristic and the assembly characteristic.
Further, in the high pressure fuel pump, if the sleeve is just clamped, its cylinder form tends to be easily deformed. Therefore, a slit is formed between a clamping portion of the sleeve and the cylinder. The slit prevents the deformation caused by clamping cylindrical clamping members from affecting the cylinder form.
However, the clamping bolt for clamping the sleeve requires a relatively large initial, axial force. This is because the initial, axial force includes not only the axial force required for sealing the intermediate member but also requires the axial force required for coping with changes in the axial force resulting from fuel pressure pulsation that is produced when the high pressure pump is operated. Therefore, taking into consideration the change in the axial force of the high pressure pump, the intermediate member must be clamped with a relatively large initial, axial force when manufactured. However, when the intermediate member is clamped by a large initial, axial force with the clamping bolt, deformation of a sealing surface of the intermediate member or deformation of the cylinder form occurs. It is difficult to prevent such distortion.